The present invention is directed to a positioning control device for guide members powered by piston-cylinder assemblies for guiding the side edges of strip at the entrance into a hot-rolled wide strip finish rolling mill train. The guide members are displaceable transversely of the rolling direction. The control is effected by comparing continuously supplied measured values of the strip position within the finish rolling train with preset required values and generating a setting or adjustment signal for each position regulating circuit assigned to the piston under assemblies so that an appropriate displacement of one or both of the guide members can be effected.
Positioning control devices of this general type are based on the knowledge gained from practical experience in that the strip position in the finish rolling trail is identical with the shape and position of the rough strip. In other words, straight rough strips have an appropriately straight and sound strip run if the finish rolling train is properly set with the guide members only holding the strip and any drifting of the strip side edges against the guide members causes the strip to run off. Guidance members for the side edges of the strip arranged ahead of the first roller stand of the finish rolling train has a definite influence on the run of the strip through train, it can influence the position of the strip and thus the passing of the strip through finish rolling train.
In one known arrangement of a positioning control of this type set forth in German Offenlegungsschrift 31 16 278, the side edges of the hot rolled wide strip, prior to passing into the first stand of the finish rolling train, are directed by guide rollers movable in slide guides transversely of the rolling direction. The sliding movement in the guides is effected by adjustment motors which are components of the positioning regulation circuits. With these adjustment motors it is possible to counteract any displacements of the run of the strip from its normal track before such displacement becomes apparent, since the comparative evaluation of the measuring results transmitted from the measuring devices located within the finish rolling train, determines a tendency of the strip to run from the normal path in sufficient time so that a counteracting positional change can be effected by displacing the guide rollers. This known device utilizes specially elastically deformable transverse beams, which at small elastic deformations trigger signals by means of strain measuring gauges when the pressure on the side edges of the rolling strip exceeds predetermined values.
Such positioning control has proved effective for the side guidance of essentially normal rough strips. Difficulties occur, however, when the end of a rough strip is wider than its nominal width. In such a situation, the end of the rough strip is forced by the first finish stand through the side guidance and may stress the guidance members to a multiple of the normal load. As a result, large deformations can occur on one of the side edges of the strip and this may possibly lead to buckling of the strip. Further, such excessive load can lead to large axial reaction forces in the supports for the rollers of the first rolling stand in the finish train. Such reaction stresses occur if the strip end is curved along one side edge. In such a situation, the strip end abuts along the side edge at one of the side guidance members and presses against it with a comparatively greater force. The reaction forces must be absorbed by the axial support of the rollers in the first rolling stand of the finish train and can lead to damage of the supports. The known position control devices do not react to such conditions, or they react in an incorrect manner, since the indicated position of the strip is correct for the measuring devices within the finish rolling train and the possibly existing measuring devices merely indicate the excess of the predetermined required value for the side pressure and cause the generation of correction signals for the restoration of the straight run of the strip.